The invention relates to a fuel filter housing for use with an automobile.
It is known from automobile construction for example, specifically in the field of fuel filters, to make the pot-shaped base of the filter housing from plastic. Lower manufacturing costs and weight savings are realized by contrast with the conventional metallic filter housings previously used. The lid is usually made in the form of a screw connection and is screwed directly to the base without any additional screws or the like, with the base and lid having matching external and internal threads.
Depending on the operating pressure that prevails in the filter housings and depending on the temperatures that prevail in the environment of the filter, the dimensional stability of the plastics used can decrease, causing deformation and hence a slight expansion of the base. The base can be reinforced areawise radially by the additional structural elements provided, such as flanges, connections, and the like, so that the expansion of the base takes place nonuniformly and therefore leads to out-of-roundness of the base with a basically round base cross section- As a result, the tightness between the base and the lid can be adversely affected.
It is known that reinforcements in the form of tensioning rings can be provided externally on the base in the sealing area of the base and lid. The term "sealing area" refers to the zone in which the reinforcements may be located and thus influence the rigidity of the base at the point where it is sealed off from the lid. These sleeve-like reinforcements in the form of tensioning rings increase the assembly costs for the filter housing. In addition, such sleeves fit uniformly around the circumference of the base so that the forces arising from inside, because of the partial reinforcement of the base by means of the other parts such as the flange, connections, and the like, can still produce an out-of-roundness of the base that is slightly reduced by the reinforcing measure.
Other reinforcing measures can consist in inserting reinforcing rings into the housing wall of the base, but these inserts result in higher production costs and can conceal the danger of material impurities or nonuniformity that can be disadvantageous for the recyclability of the filter housing.
A housing according to the species is known from DE-OS 28 31 070 (FIG. 6). A lid with corners is provided on a round base. The base has a circumferential rib in its uppermost area close to the lid, said rib following the contour of the lid. Projections relative to the base result at the corners so that screws can be provided there to join the lid to the base, since the lid itself is not designed as a screw closure.
Connecting stubs terminate in the base close to and below the circumferential rib on two opposite sides. When the rib follows the contour of the lid, a circumferential rib has a reduced cross section not only above the connecting stub, but also at other points opposite the round base, so that the intrinsic stiffness of the base relative to pressure stresses arising from inside is not uniform around the circumference. As a result, depending on the choice of material and the wall thickness of the base, fluid leaks between the base and lid can result.